Notes, summaries, assignments, exams, and problems for Computers

Data Link Protocols

LAPB, LAPF, and LAPD

These are Data Link protocols:

• LAPB (Link Access Procedure, Balanced): A subset of HDLC, providing asynchronous balanced mode (ABM) for point-to-point links between user systems and packet-switching network nodes.
• LAPF (Link Access Procedure for Frame-Mode Bearer Services): Includes a control protocol (similar to HDLC) and a core protocol (subset of the control protocol). LAPF control uses ABM and 7-bit sequence numbers. LAPF core has flag, address, information, and FCS fields, but no control field.
• LAPD (Link Access Procedure, D-Channel): Provides data link control over the ISDN D channel. Uses ABM, 7-bit sequence numbers, a 16-bit CRC FCS, and a two-part address field for device and logical user identification.

Oracle Tablespaces and Data Storage

System tablespaces and the required sysaux tablespace are created when the database is created and must be online.

The System tablespace is used for core functionality, for example, the data dictionary tables.

The auxiliary Sysaux tablespace is used for additional database components, such as the Enterprise Manager repository.

A tablespace accounts for one or more data files.

Data files belong to one tablespace.

User process: It begins when the user database server requests a connection to Oracle.

Process server: Connects to the Oracle instance and starts when a user establishes a session.

Background processes: Start the Oracle instance.

Oracle is a server management system database that provides an open, comprehensive,... Continue reading "Oracle Tablespaces, Segments, and Data Blocks Explained" »

Understanding Computer Memory

Memory Types

Main Memory

Main memory is integrated into the system's firmware and directly governed by the CPU. It stores the boot process, data from the stack, memory-resident programs, and the user program currently executing.

Types of Main Memory:

• Ferrite memories (obsolete)
• Integrated memory:
  • RAM (Random Access Memory)
  • ROM (Read-Only Memory)
  • PROM (Programmable ROM)
  • EPROM (Erasable Programmable ROM)
  • OTP Memory (One-Time Programmable ROM)
  • EAROM (Electrically Alterable ROM)

Cache Memory

Cache memory is located within the CPU and communicates directly with it. It stores frequently used data to reduce access time from main memory.

Mass Memory

Mass memory refers to storage devices with higher capacity, typically peripherals.

Types

Client-Server Model

• The client-server model defines the structure of communicating applications and their synchronization.
• It consists of two interacting processes:
  • Server Process
  • Client Process
• Client and server are inseparable; one cannot exist without the other.

Server

• This process awaits hearing on a given server port. It continuously waits for remote client processes to connect.
• Authentication
• Security and information privacy in the system where they reside.
• Must be able to handle requests from multiple clients simultaneously.
• Important: All clients will be connected to the same server port.

In general, we say that a computer is a server when its operating system runs one or more server processes (FTP, HTTP, DNS, etc.).

Client

• It is a process that sends

Video Capture and Storage

Factors Affecting Video Capture Speed

Which of the following is not a factor in the loss of speed in video capture to your computer?

• CD/DVD speed

Recommended Hard Disk Data Transfer Rate

For video capture, the recommended minimum hard disk data transfer rate is:

• 2.5 Mb/sec
• 5.0 Mb/sec
• 4.5 Mb/sec
• 3.5 Mb/sec

Peak Writing Definition

The amount of information a hard drive can write consistently in one second is called Peak Writing.

Data Compression

Compression Process

Compression is the process of removing or restoring data to reduce the size of a file.

Synchronous vs. Asynchronous Compression

When the algorithmic compression process takes the same amount of time as the decompression process, it is called Synchronous.

Audio Formats and

Matrix Operations and Linear Equations in MATLAB

Format short, long format, format rat (format is the x / y), format short (as is 3 * 10^-5 = 3e-5). A = [; ;]. To extract a positive one: A(2,2). Changing a number in one position: A(row, column) = number in that position.

Write a whole line: A(row,:). or A(row, 2:4) - the columns you want from that row. For columns it is the same but in reverse: A(:, 3:7). Extract a submatrix A(2:3, 2:3) - ever-growing range. Transpose: A.'. Conjugate matrix (star A*): A'. Matrix for blocks: [A | E] - like n-th row or [A; E] - so I place it under.

Matrix by number unit: 23 * ones(3). Identity: eye(x, y).

Systems of Linear Equations Ax = b:

• Rank(A) = rank(A | b) = No incog. - SCD: x = A \ b
• Rank(A) = rank(A | b)

Components

DNS Client, DNS Servers, Zones of Authority

Transport Layer Model: TCP/IP

TCP

The Transmission Control Protocol (TCP) ensures reliable communication between the sender and receiver of a message.

UDP

The User Datagram Protocol (UDP) offers a lower guarantee of packet delivery compared to TCP because it doesn't use acknowledgments.

Implementation Level of the TCP/IP Model

The application layer is the level where common programs communicate over a network.

ICMP

The Internet Control Message Protocol (ICMP) is a sub-protocol for diagnostics and error reporting within the Internet Protocol (IP).

FTP

The File Transfer Protocol (FTP) is part of the TCP/IP suite and provides file transfer services.

HTTP

The HyperText Transfer Protocol (HTTP) is the foundation... Continue reading "TCP/IP Model and Comparison with OSI Model" »

Media Player Functionality

A media player can play both audio and video, including TV programs. Common widget types include:

• DVD (xine)
• Audio (Winamp)
• Video (Windows Media)
• Multimedia (Movie Player)

FLV Format

FLV is a streaming video format popular on the internet, especially due to platforms like YouTube and Google Video. It requires Adobe Flash Player.

Video Editing Process

Video editing encompasses all operations performed during movie production.

Movie Components

Key components of a movie include:

• Menu
• Movie
• Frame
• Transition
• Clip

Windows Movie Player

Windows Movie Player is a built-in Windows application for simple and comprehensive video editing.

Film Editing

Film editing involves inserting various clips in chronological order for viewing.

Mounting Process

The... Continue reading "Media Player, Video Editing, and Movie Production Essentials" »

Here's a list of essential Linux commands:

• lime - Displays the current calendar.
• lime 1980 - Shows the calendar for the year 1980.
• cal 12 1980 - Displays the calendar for December 1980.
• date - Displays the current date.
• date -s "2009-11-05 18:55" - Changes the system time.
• who - Shows who is currently logged into the system.
• who -u - Displays the process ID (PID) of logged-in users.
• kill -9 3525 - Terminates the process with PID 3525.
• uname - Outputs the machine's name.
• uname -a - Shows detailed information about the machine.
• uptime - Displays how long the machine has been running.
• du - Displays disk space usage by folders.
• du -k - Displays disk space usage in 1024-byte blocks.
• df - Displays disk usage statistics.
• ps - Displays a general list of running processes.

Users

• Creation

From the Partner's Computer

• Create user `Professor` @ '192.168.5.25' identified by 'Professor';

Local Access

• Administrative user `Create` @ 'localhost' identified by 'Administrative';

Access from Any Computer

• Create user `` @ '%' student identified by 'student';

• Deletion

• DROP

• Permissions

To Grant Permissions

• GRANT SELECT ON clase.cuidadores TO 'student'@'localhost';

SELECT * FROM carers;

• GRANT SELECT (name, currency) ON clase.cuidadores TO 'student'@'localhost';

SELECT name FROM currency carers;

• GRANT INSERT, SELECT, UPDATE ON IES.Curso TO 'Administrative'@'localhost';

• GRANT INSERT (IdCurso, DNI), SELECT (IdCurso, DNI), UPDATE (IdCurso, ID) ON IES.Matrícula TO 'Administrative'@'localhost';

With Update

• GRANT SELECT (name, currency), UPDATE (currency)